(defun make-something
(typ pname x-pos y-pos x-speed y-speed)
(let ((ins (make-instance typ)))
(set-pname ins pname)
(set-x-position ins x-pos)
(set-y-position ins y-pos)
(set-x-speed ins x-speed)
(set-y-speed ins y-speed)
ins))
という形で行ないます．